Can RTV Sealant Help The Performance Of Your Direct Vent Fireplace

BY Collin Champagne Feb 22, 2023

If you have a direct vent fireplace with poor performance quality; like low flames, excess soot or random flame outage; you may have missed a critical component during installation. Mill Pac is a brand of high-temperature sealant, similar to a silicone sealant, that is applied to venting for direct vent fireplaces.

It helps to seal connections or any other places where air may leak out. Mill Pac is a widely used and trusted brand of sealant because it has a less rubbery consistency and higher temperature rating than many others.

Though it is very important to use a RTV sealant, or fire caulk as some call it, you could opt for Rutland Seal It Right, as a more affordable but still quality alternative. The most important thing to understand is that if the fire caulk was not applied at the original installation, you may end up with gas leaking from the exhaust pipe into the intake air pipe. If that leak is bad enough, it can be the culprit behind your poor fireplace performance.

It's absolutely necessary for the sealant to be applied at the flue collar and anywhere flex vent pipe meets a stationary piece of pipe. If you are joining flex piping to a rigid coupler or transitioning to a rigid section through the roof or wall, its suggested to use the sealant to make sure the flex pipe doesnt lose its grip.

Though it isnt required, there are other areas of direct vent piping that may benefit from applying a generous layer of the flexible material. The similar structure of RTV sealant to silicone sealant is what helps to secure the connection of the vent piping.

: mill pac sealant

The sealant comes in convenient sizes like 10.1 or 10.3 ounce tubes that fit into a standard caulking gun. So, this makes set up and installation that much easier. RTV sealant often has around a 12-month long shelf life which ensures you get the most product for your money.

If you have any other questions about the uses and purpose of sealant, feel free to reach out to our NFI certified techs at 800.203.1642.

About the Author

Collin Champagne

With over 13 years in the industry, Collin is a National Fireplace Institute (NFI) certified technician and managed content for the eFireplacestore and eCanopy brands. He has achieved the highest NFI certification possible as a Master Hearth Professional and is certified in all three hearth appliance fields: wood, gas, and pellet. With experience with sales and in-field installations, his expertise shines through his technical knowledge and way with words.